Electrical feed-through assemblies serve the purpose of providing an electrical circuit path extending from the interior of a hermetically sealed container to an external point outside the container. A conductive path is provided through the feed-through assembly by a conductive terminal pin that is electrically insulated from the container. Many such feed-through assemblies are known in the art that provide the electrical path and seal the electrical container from its ambient environment. Such feed-through assemblies typically include a ferrule, the terminal pin and an insulating member that supports the pin within the ferrule. Such feed-through assemblies often are used in an electrical implantable medical device (IMD) such as an implantable drug pump and an implantable pulse generator (IPG) including cardiac rhythm management devices, deep brain stimulators, nerve stimulators and the like. Herein all such devices, including electrochemical cells, are intended to be encompassed under the rubric of the abbreviated IMD. The reliability of an IMD depends, in large part, on the hermetic sealing of the various components of the feed-through assemblies. The hermetic sealing may be achieved by brazing the components of the feed-through assembly using a brazing metal or alloy.
Brazing of feed-through assemblies typically includes assembling the components of the feed-through assemblies on a brazing fixture and inserting the brazing fixture in a furnace that subjects the feed-through assembly components to high temperatures, usually in excess of 500° C. Because of the high temperatures at which brazing occurs, brazing of feed-through assemblies poses significant challenges. Depending on the material from which the brazing fixture and the ferrule is fabricated, the ferrule may bond to the brazing fixture during brazing, making the feed-through assemblies difficult to remove from the brazing fixture. Moreover, materials of the brazing fixture may chemically react with the terminal pin, thereby reducing the melting point of the terminal pin and causing the terminal pin to melt during brazing.
Accordingly, it is desirable to provide a brazing fixture for the fabrication of feed-through assemblies that reduces the likelihood that a feed-through assembly will bond to the brazing fixture during brazing. In addition, it is desirable to provide a brazing fixture that will not reduce the melting point of the terminal pin of the feed-through assembly during brazing. It is also desirable to provide a method for fabricating an improved brazing fixture. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.